The present invention relates to number portability (NP) in telecommunication networks, and more particularly to systems and methods for number portability call processing.
Currently, local phone service is provided by a single company, such as a Regional Bell Operating Company (RBOC). These companies basically enjoy a monopoly over local phone service within their regions. Thus, efforts are being made to introduce competition into the local phone market to eliminate the monopolies. Under the current system, however, if customers want to change from one service provider to another, they must also change their phone numbers. This is a serious deterrent to switching service providers and, thus, a hindrance to free and open competition.
To alleviate the problem, the Federal Communications Commission (FCC) has issued an order for NP which, in addition to providing other features, will allow a customer to switch between local service providers while keeping the same phone number.
The public telephone network consists of a large number of switches, such as Lucent Technologies' 5ESS, each serving about 10k-100k customers. When a customer dials a number, the customer's serving switch (the originating switch) must allocate a route to the switch serving the dialed number (the destination/provider switch). In the existing pre-NP telephone network, the first six digits (NPA-NXX) of a 10 digit phone number identify a particular switch in a particular geographic region. Switches can route calls between switches based on the NPA-NXX of the dialed number. In an NP environment, however, this relationship between the NPA-NXX and the physical location of a switch is broken, such that there is no fixed relationship between a dialed number and its geographic location.
Current proposals for NP involve storing an identifier corresponding to the switch to which a subscriber's service has been ported in large, special purpose computers, known as service control points (SCP). A simple way to implement NP is for a switch to simply query an SCP for a routing address on every interswitch call, a procedure known as "N-1." However, since most numbers are unported, i.e., most customers stay with one provider, N-1 results in many unnecessary SCP queries. An alternative procedure is to first route the call to the dialed subscriber's original provider switch. If the dialed subscriber's number has been ported, the original provider switch releases the call (i.e., the original provider switch sends a release message to the originating switch). The originating switch then queries the SCP to find out the identifier of the switch providing service to the ported, dialed subscriber. This procedure is called Query-on-Release (QOR). Both the N-1 and QOR procedures suffer from inefficient use of network resources when used to provide number portability.
The present invention can be implemented in a variety of telecommunication networks including, for example, a telephone network as depicted in the block diagram of FIG. 1. As shown in FIG. 1, a telephone network typically includes a plurality of switches A, B, and C connected by switched telecommunications network (STN) 106. For purposes of this description, these switches are designated as originating provider switch A 102, original provider switch B 108, and ported provider switch C 112. Each switch supports numerous subscribers such as telephone service subscribers 100 and 110. In a typical call flow in such a network, subscriber 100 dials a destination telephone number corresponding to subscriber 110; for example, 201-576-6123. Processing this call according to the QOR procedure, switch A 102 routes the call through STN 106 according to the NPA-NXX of the dialed number, i.e., 201-576, to original provider switch B 108 without first querying SCP 104 for a routing translation of the dialed number. The last four digits of the dialed number, i.e., 6123, identifies a specific telephone line number of Switch B 108. Note that there are also switches that support greater than 10,000 phone numbers. Switch B 108 connects the incoming call to line 6123, thus completing the call to subscriber 110.
Number portability means that subscriber 100 will not need to use a new telephone number to call subscriber 110 if subscriber 110 changes service providers or relocates to an area served by a different switch owned by their current provider. In other words, once a provider assigns a telephone number to subscriber 110, this number remains the subscriber's telephone number regardless of the company providing telephone service to the subscriber or geographic location of the switch actually serving the subscriber. Once subscriber 110 changes from service provided by a telephone company owning switch B 108 to a company owning switch C 112, the company owning switch C 112 is known as a "ported provider" and the telephone number of subscriber 110, which remains the same, is a "ported number." In the example depicted in the block diagram of FIG. 1, ported subscriber 110 receives telephone service from line 1234 of switch C 112. The ported number represents a virtual address of the switch providing service and cannot be used to route calls without translation to obtain the identifier of the switch actually providing service to "ported subscriber" 110.
The difference between routing calls using the N-1 call processing procedure and the QOR call processing procedure is a matter of timing. Specifically, N-1 and QOR are distinguishable by considering the timing of when ported number translation occurs. Under QOR the originating provider processes every number dialed by subscriber 100 as if the number were not ported and attempts to route the call to switch B 108 having switch identifier 201-576. However, if subscriber 110's service is ported to switch C 112, original provider switch B 108 will release the incoming call. Upon receiving a signal from switch B 108 that the attempted call to subscriber 110 through switch B 108 was released, originating provider switch A 102 queries a routing translation database in SCP 104 for a translation of the dialed number to obtain the identifier of the ported provider switch. SCP 104 translates the dialed ported number 201-576-6123 to a route corresponding to switch C, line 1234. Accordingly, the call is properly routed to ported subscriber 110 through ported provider switch C, thus completing the call.
In contrast to QOR call processing, a switch executing the N-1 procedure assumes each dialed number is a ported number and requests a translation of the dialed number from the SCP before attempting to complete the call. Overall, the QOR procedure is inefficient because it attempts to complete calls to switches that no longer provide service to a particular subscriber. The N-1 procedure is inefficient because the originating switch queries the SCP for numbers that have not been ported.
Accordingly, it is an object of the invention to improve the efficiency and effectiveness of NP call processing procedures.